PROJECT SUMMARY This K08 research and training award will enable the PI to attain the substantive and methodological expertise necessary to conduct independent research on nicotine use in young adults and to translate this knowledge to clinical trial development. Dual use of electronic nicotine delivery system (ENDS) and combustible cigarettes is the most prevalent pattern of tobacco use among US young adults (age 18?25). Characterizing shared, distinct, and cross-conditioned processes that maintain dual use is essential for informing interventions against smoking among vulnerable dual users. The incentive sensitization and affect processing models of drug addiction highlight how drug cues and attentional bias for cues are central drivers of drug craving and use and how negative affect strengthens these relationships. I propose to examine the degree to which these three processes (cue-reactivity, attentional bias, and negative affect) underlie tobacco craving and in laboratory and naturalistic settings among a sample of young adult dual users (n = 80). Significant innovations include examining cross-product conditioning of cues in young adult dual users; integrating data across laboratory and naturalistic settings; and identifying shared and distinct processes in ENDS versus combustible cigarettes. I will examine the effects that in-vivo neutral, ENDS, or combustible cigarette cues have on craving for usual-brand cigarettes or preferred ENDS devices in three laboratory sessions. A visual probe task will index attention bias; participants will self-report positive and negative affect. EMA will be used to gather real-time data from the same participants evaluating predictors of tobacco use and craving that correspond to laboratory measures (mood, tobacco cues), as well as salient social and behavioral correlates. Person- and event-level effects of cue reactivity, attentional bias, cross-product conditioning, and the interactive effect of negative affect will be modeled using multilevel modeling. Results will elucidate the contribution of attentional, mood, and cue-related processes to craving and dual use. Findings will inform development of two research projects: a longitudinal study using survey, EMA, and laboratory methods to characterize the intra-individual behavioral processes underlying transitions through smoking patterns (especially progression from ENDS to dual user); and preparation for a clinical trial of a novel just-in-time adaptive intervention (JITAI) targeting dual users who are either high or low in markers of vulnerability (e.g., cross-product reactivity). A final series of focus groups will assess the receptivity and acceptability of prototype study-informed JITAI components. Highly skilled mentors, including Kristina Jackson, Suzanne Colby, Andrea King, Tyler Wray, and Rachel Cassidy and collaborator Christopher Kahler will provide guidance on training aims: (1) behavioral laboratory assessment methods; (2) analysis and integration of laboratory and naturalistic data; and (3) translation of laboratory findings to JITAI. Overall, the research and training outlined in this application informs key gaps in models of tobacco dual use, and will prepare the PI to conduct independent research furthering scientific inquiry in this field.